Phase formation of PrFe11V1-xTix and CeFe11V1-xTix compounds with the ThMn12-type structure has been investigated by x-ray diffraction (XRD), differential thermal analysis (DTA) and ac initial susceptibility. The stable temperature range of the 1-12 phase for PrFe11V1-xTix alloys has been constructed as a function of Ti content. It is found that the PrFe11V compound with the ThMn12-type structure do not form. The PrFe11Ti compound with the ThMn12-type structure can only be obtained by annealing at a narrow temperature range between 1030 degrees C and 1113 degrees C. Furthermore, 1-12 phase can be obtained at lower temperature and wider temperature range with decreasing Ti content x(0.2 less than or equal to x less than or equal to 1). The CeFe11V and CeFe11Ti compound with ThMn12-type structure can be synthesized, and it is more favorable to synthesis the 1-12 single phase for the pseudotenary CeFe11V1-xTix compounds. For PrFe11V1-xTix compounds with x = 0.2-1, the lattice parameters a and c do not vary very much: around 0.860 and 0.479 nm, and Curie temperature T-c is 268 degrees C-329 degrees C. For CeFe11V1-xTix compounds the lattice parameters a and c are around 0.857 and 0.478 nm, and Curie temperature T-c is 211 degrees C-252 degrees C.